The present invention relates to an integrated liquid metal-cooled fast neutron nuclear reactor comprising a liquid metal-filled vessel, which is sealed in its upper part by a reinforced concrete boxed slab acting as a support for the exchangers and the pumps of the primary circuit.
In such reactors, the assemblies constituting the core rest on the bottom of the vessel or on the periphery thereof via a liquid metal (generally sodium) supply support and a flooring. The liquid sodium is heated in the core by the fission reaction of the nuclear fuel before entering a hot collector placed above the core and in heat exchangers, where it transfers its calories to the fluid (generally sodium) circulating in secondary circuits. The cold primary sodium leaving the cold collector located in the lower part of the exchangers is sucked in by primary pumps, which reinject it into the support. In this type of reactor, the exchangers and primary pumps are generally suspended on the slab sealing the reactorvessel. This is also the case with a certain number of other members necessary for the operation or safety of the reactor.
In reactors such as the Phenix or Super-Phenix, the assemblies are periodically removed from the core by a transfer arm or by pokers or rabbles mounted on rotary plugs, followed by discharging by means of a ramp and lock system into an adjacent storage enclosure, where they discharge their residual power for an adequate time to at least partly deactivate the same. They subsequently undergo processing for separating the canning material from the fuel for the purpose of recovering the latter.
This handling system is relatively complex and particularly in the case of fissile assemblies, it is made difficult to carry out by the presence of instrumentation which is suspended on the plug-cover-core.
French Pat. No. 7,131,036 filed on 26.1.1971 by the Commissariat a l'Energie Atomique and Creusot Loire proposed simplifying the handling system and facilitating its performance in the case of fissile assemblies, by equipping the reactor with a tight cell into which the plug-cover-core could be retracted, so as to free the top of the core for the passage of a handling arm.
The idea of a tight cell for the retraction of the plug-cover-core was also envisaged in British Pat. No. 1,026,559 filed by the U.K.E.A. and was previously investigated on a SEFOR reactor mockup in the USA (GEAP 5701, AEC Research and Development Report, March 1969).
However, the installation of a handling cell on the slab of an integrated fast neutron nuclear reactor has never been seriously considered, because it was generally believed that its construction would either lead to overdimensioning of the reactor and consequently to increased cost, or to a reduction in the power for constant dimensions. Moreover, the realization of this solution is only possible on a sufficiently rigid, strong slab and this is not the case with the mechanically welded slab of the Phenix and Super-Phenix reactors.
In addition, European patent publication No. 0058583 published Aug. 25, 1982 by the Commissariat a l'Energie Atomique proposed a very rigid, strong slab, with no significant increase in costs.